early 15c., "action of entangling," from Latin implicationem (nominative implicatio) "interweaving, entanglement," from past participle stem of implicare "involve, entangle, connect closely," from assimilated form of in- "into, in, on, upon" (see in-(2)) + plicare "to fold" (see ply, v.1). Meaning "something implied (but not expressed)" is from 1550s.